Conventional pulse/Fourier-transform NMR spectrometers are generally capable of performing a wide variety of magnetic-resonance measurement sequences. Such magnetic-resonance measurement sequences typically involve subjecting a sample in a magnetic field to pulsed or otherwise time-varying radio-frequency fields at one or more frequencies; amplifying, detecting, and digitizing the magnetic-resonance signals elicited from the sample by the radio-frequency fields; and processing the resulting digitized signals by Fourier transformation or other data processing operations for analysis and display. As used herein, the term "magnetic-resonance measurement sequence" can refer to sequences in which two or more operations in a magnetic resonance experiment which are carried out simultaneously--such as, for example, simultaneous irradiation of a sample at two frequencies--as well as operations which follow one another in time.
A conventional pulse/Fourier-transform NMR spectrometer ordinarily includes a radio-frequency pulse-generator/transmitter and a pulse programmer for controlling the pulse-generator/transmitter to produce sequences of radio-frequency excitation pulses. In general, each pulse in such a pulse sequence has a well-defined shape, intensity, duration, phase, and separation from neighboring pulses. Different pulse sequences are generally required for different magnetic-resonance measurement sequences.
A magnetic-resonance measurement sequence also typically involves digitizing at timed intervals the magnetic-resonance signals excited by the sequence of radio-frequency pulses, accumulating digitized signals from a number of measurement runs for signal averaging, and digitally manipulating the accumulated digitized signals by Fourier transformation or other algorithm. For this reason, conventional pulse/Fourier-transform NMR spectrometers generally include a data processor which may be programmed to perform specified data-processing operations to analyze the magnetic-resonance signals excited by a particular pulse sequence.
Among the factors which can influence the selection of a particular pulse sequence and a particular set of data processing operations is the nature of the sample to be investigated. Thus, each time a new sample is introduced into the NMR spectrometer for analysis, it is ordinarily necessary for a user to enter instructions into the spectrometer specifying the measurement sequence to be used. NMR spectrometers configured for automatic operation may include an automatic sample changer for inserting a series of samples one-by-one into and withdrawing them from the spectrometer automatically. The user must ordinarily enter instructions into the spectrometer to program the operation of the automatic sample changer as well as to specify the measurement sequence to be used for each of the samples.
Modern pulse/Fourier-transform NMR spectrometers are capable of performing an almost bewildering variety and number of measurement sequences when account is taken of the many different NMR measurement experiments which can be performed and the many different nuclei and combinations of nuclei on which such experiments can be carried out. The measurement sequences to obtain the NMR spectra of different nuclei constitute different sequences since a user must specify the identity of the nucleus--or equivalently, its resonance frequency--to the spectrometer. Moreover, the number of such measurement sequences is increased inasmuch as the NMR spectra of the various nuclei can be obtained with or without the application of radio-frequency decoupling fields for effectively eliminating interactions with other types of nuclei in the sample. The number of measurement sequences for obtaining NMR spectra is further increased in that additional radio-frequency fields may be applied to suppress interfering resonance lines from solvents in which the sample is dissolved. Different measurement sequences are required to determine relaxation times of individual resonance lines using sequences of pairs of radio-frequency pulses of differing widths--for example, a 180.degree. pulse followed by a 90.degree. pulse--and incrementally varying the time interval between the pulses of the pair. In still other measurement sequences of which many modern pulse/Fourier spectrometers are capable, two-dimensional spectra may be obtained which reveal interactions between different nuclei in a sample. Polarization may be transferred from one group of nuclei to another by measurement sequences such as an experiment referred to as the distortionless enhancement by polarization-transfer experiment--also referred to as the "DEPT" experiment. In general, a user must specify which of these and many other measurement sequences the pulse/Fourier-transform spectrometer is to perform on a sample in a given experiment.
In addition, conventional pulse/Fourier-transform NMR spectrometers are capable of locking the magnetic field of the spectrometer to resonance signals of a variety of nuclei in a locking channel. Optimizing the locking typically involves adjusting parameters such as the power of a radio-frequency field in the locking channel of the spectrometer, the gain of a receiver in the locking channel and the phase of a magnetic-resonance signal used for locking. A user must ordinarily specify at least the nucleus and compound from which the locking signals are to be obtained, and, in many spectrometers, may specify the values of the locking-channel parameters as well.
To produce a highly homogeneous magnetic field typically required in magnetic resonance spectroscopy, currents through various magnetic-shim coils must be adjusted. Modern high-resolution magnetic-resonance spectrometers in general perform such field shimming adjustments automatically. However, different samples and different experimental procedures may require different strategies for optimizing the shimming. Consequently, the user may have to specify the shimming procedure to be used in a given experiment.
A user is faced with additional parameters to specify which relate to collecting magnetic-resonance signal data in specifying a measurement sequence for a conventional pulse/Fourier-transform NMR spectrometer. For example, the phase, the gain, and the bandwidth of a receiver channel of the spectrometer must be specified for each measurement sequence. In addition, the interval between the times the signal is sampled must be specified.
The user of a pulse/Fourier-transform NMR spectrometer must provide further specifications in connection with processing the digitized magnetic-resonance signals for the display and analysis. For example, the user typically must specify selections for the measurement sequence in connection with correcting phase errors, compensating for base-line drift, and defining regions for integrating line intensities. In addition, the media on which the resulting spectra are to be displayed must be specified, along with scaling parameters and whether or not spectral lines will be identified digitally.
Largely as a result of the great number of different items which a user must specify in performing even routine magnetic-resonance measurements on a modern pulse/Fourier-transform NMR spectrometer, such spectrometers tend to be intimidating to users who may desire the results of magnetic-resonance measurements, but who are not experts in magnetic-resonance measurement technology.
Attempts have been made in the past to simplify the operation of NMR spectrometers so that magnetic- resonance measurements could be carried out by persons who are not expert in magnetic-resonance measurement technology. In certain cases such attempts have simplified spectrometer operations somewhat, but there remains room for improvement.
For example, a series of pulse/Fourier-transform NMR spectrometers commercially available from Bruker Instruments Inc. of Billerica, Massachusetts under the trade designation "AM"-series spectrometers has been capable of performing a variety of magnetic-resonance measurements on a number of different nuclei. Each "AM"-series spectrometer has included a computer for controlling the spectrometer as well as for storing and processing the signals obtained from the magnetic-resonance experiments. Software has been available for the computer which, on the one hand, has allowed a specialist in magnetic-resonance measurement technology to have access to the full range of the capabilities of the spectrometer, and which, on the other hand, has permitted less-experienced users to perform routine experiments without requiring them to specify the details of spectrometer operation. A menu of descriptive information has been provided which was invoked by typing a "HELP" command on the keyboard. A menu-driven procedure has been available for specifying experiments for obtaining routine NMR spectra--including certain two-dimensional spectra which directed the user to supply necessary spectrometer-control instructions through a dialogue procedure. The selected spectrometer-control instructions served to invoke control routines in the computer for controlling the operation of the spectrometer. Appropriate sets of parameters were retrieved from a magnetic disk for performing the specified experiment.
For entering spectrometer-control instructions from a user, the "AM"-series of NMR spectrometers have heretofore included a terminal in form of a console having a keyboard, a display and an interface/control system. The display of the terminal was capable of displaying the menu of instructions from which the user could select by typing on the keyboard and displaying the instructions so selected. However, the typing of a series of spectrometer-control instructions tended to be an exacting task which too often led to errors. Although certain typing errors could be detected and rejected by the terminal interface/control system when they were recognizable as syntax errors, correctly-typed, but inappropriate instructions could not in general be detected and tended to cause trouble since such instructions could launch the spectrometer on sequences of inappropriate operations.
A mouse for controlling the position of a cursor on the display has also been available for spectrometer-control instruction input in the "AM"-series of spectrometers. Another conventional pulse Fourier-transform spectrometer has employed a light pen and a CRT for entering spectrometer-control instructions. A conventional magnetic-resonance tomographic imaging device heretofore available has used a touch-sensitive CRT for entering instructions for controlling the device.
The computer software for the "AM"-series of NMR spectrometers also includes a password system which is intended to prevent one user from accessing or destroying the files of another user. In addition, the software password system is programmed to prevent users other than a designated system manager from altering the system software and the basic interface between the software and the spectrometer. However, if an unauthorized person learns the password of the system manager, the person can be in a position to make changes to the fundamental system software and software/spectrometer interface without the system manager's knowledge. Moreover, even an inexperienced user using his or her own password is permitted to bypass the menu-driven procedure for routine experiments and directly alter spectrometer settings and experimental parameters. A subsequent user can experience error, confusion, and delay when a prior user changes spectrometer settings and experimental parameters to nonstandard values and does not return them to expected standard values prior to leaving the spectrometer for the subsequent user.
Among the features heretofore available on the Bruker "AM"-series NMR spectrometer was an automated sample changer. The sample changer had an array of sample holders for holding sample tubes containing samples to be analyzed. The sample tubes were labelled with barcoded labels. The sample changer included a barcode reader mounted on the changer which was capable of reading the labels of the sample tubes one at a time. The sample changer was adapted to transfer selectively a sample tube identified by a predetermined label to the magnet.
European published patent application No. 86302595.3, published Oct. 15, 1986 under publication No. 0197791, disclosed an automated apparatus for presenting samples to an NMR spectrometer. The apparatus employed a reflective coding label affixed to a sample carrier for identifying the sample and prescribing the operating parameters of the spectrometer. An LED light source and a photodiode optical detector were mounted in the probe of the spectrometer adjacent to a sample-carrier-receptacle cavity for reading the reflective coding labels of sample carriers inserted in the cavity. Evidently, to make any change in the operating parameters prescribed by a reflective coding label for a sample required the preparation of a new reflective coding label, removing the label previously affixed to the sample carrier, and affixing the new label in place of the previous label, a major inconvenience.